feat: kit-connect + syno-balance SPK builds, busfleet hub registration endpoint

- kit-connect SPK (ipq806x): postinst with hub registration, start-stop-status,
  connect-daemon management, Tailscale + reverse SSH tunnel integration
- syno-balance SPK (noarch, test build): SmartWAN-aware dual-WAN load
  balancer with 6-factor scoring engine, syno-daemon lifecycle
- Busfleet hub: register.sh (port pool 2230-2299), Python HTTP server,
  systemd service, port-registry.json with x4078/x5925 assignments
- .gitignore: exclude SSH keys (*_id_ed25519), SPK artifacts (*.spk)

Gitea releases:
- kit-connect v0.1-0001 → x5925-kit-connect-v1 (production)
- syno-balance v0.1-0001 → syno-balance-test-v1 (prerelease)

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

.gitignore

@@ -0,0 +1,12 @@
+# SSH keys
+*_id_ed25519
+*_id_ed25519.pub
+*.pem
+
+# Build artifacts
+*.spk
+build/
+
+# IDE
+.idea/
+.vscode/